Electronic switches, such as MOSFETs, IGBTs, or other types of transistors are widely used as electronic switches for switching electrical loads, such as motors, lamps, magnetic valves, and the like. In these applications, the electronic switch is connected in series with the load, where the series circuit with the electronic switch and the load is connected between power supply terminals. The load can be switched on and off by switching the electronic switch on and off.
Usually, the on-resistance of the electronic switch, which is the resistance of the electronic switch in the on-state, is lower than the resistance of the load, so that in a normal operation state a voltage drop across the electronic switch is significantly lower than a voltage drop across the load, when the electronic switch is switched on. When, however, there is a short circuit in the load and when the electronic switch is in the on-state, the voltage drop across the electronic switch increases and the electric power dissipated in the electronic switch increases. The increase in dissipated power results in an increased temperature of the electronic switch.
According to a first approach for protecting the electronic switch from being damaged, the temperature in the electronic switch may be detected and the electronic switch may be switched off when the temperature reaches a given temperature threshold.
According to a second approach, a first temperature in the electronic switch and a second temperature remote to the electronic switch may be measured and the electronic switch may be switched off when the difference between these two temperatures reaches a given temperature difference threshold. Both, the first and the second approach can be applied together.
There is a need for an improved temperature protection of an electronic switch.